--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,21 @@
 2012-02-27  Bruno Haible  <bruno@clisp.org>
 
+	remainderl-ieee: Work around test failure on OSF/1.
+	* m4/remainderl-ieee.m4: New file.
+	* m4/remainderl.m4 (gl_FUNC_REMAINDERL): If gl_FUNC_REMAINDERL_IEEE is
+	present, test whether remainderl works with a zero second argument.
+	Replace it if not.
+	* lib/math.in.h (remainderl): Override if REPLACE_REMAINDERL is 1.
+	* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_REMAINDERL.
+	* modules/math (Makefile.am): Substitute REPLACE_REMAINDERL.
+	* modules/remainderl (configure.ac): Consider REPLACE_REMAINDERL.
+	(Depends-on): Update conditions.
+	* modules/remainderl-ieee (Files): Add m4/remainderl-ieee.m4.
+	(Depends-on): Add remainder-ieee.
+	(configure.ac): Invoke gl_FUNC_REMAINDERL_IEEE.
+	* doc/posix-functions/remainderl.texi: Mention the remainderl-ieee
+	module.
+
 	remainderf-ieee: Work around test failure on OSF/1.
 	* m4/remainderf-ieee.m4: New file.
 	* m4/remainderf.m4 (gl_FUNC_REMAINDERF): If gl_FUNC_REMAINDERF_IEEE is

--- a/doc/posix-functions/remainderl.texi
+++ b/doc/posix-functions/remainderl.texi
@@ -4,15 +4,22 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/remainderl.html}
 
-Gnulib module: remainderl
+Gnulib module: remainderl or remainderl-ieee
 
-Portability problems fixed by Gnulib:
+Portability problems fixed by either Gnulib module @code{remainderl} or @code{remainderl-ieee}:
 @itemize
 @item
 This function is missing on some platforms:
 FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 4.0, Solaris 9, Cygwin, MSVC 9, Interix 3.5, BeOS.
 @end itemize
 
+Portability problems fixed by Gnulib module @code{remainderl-ieee}:
+@itemize
+@item
+This function has problems when the second argument is zero on some platforms:
+OSF/1 5.1.
+@end itemize
+
 Portability problems not fixed by Gnulib:
 @itemize
 @end itemize

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -1028,10 +1028,19 @@
 #endif
 
 #if @GNULIB_REMAINDERL@
-# if !@HAVE_REMAINDERL@
+# if @REPLACE_REMAINDERL@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef remainderl
+#   define remainderl rpl_remainderl
+#  endif
+_GL_FUNCDECL_RPL (remainderl, long double, (long double x, long double y));
+_GL_CXXALIAS_RPL (remainderl, long double, (long double x, long double y));
+# else
+#  if !@HAVE_REMAINDERL@
 _GL_FUNCDECL_SYS (remainderl, long double, (long double x, long double y));
+#  endif
+_GL_CXXALIAS_SYS (remainderl, long double, (long double x, long double y));
 # endif
-_GL_CXXALIAS_SYS (remainderl, long double, (long double x, long double y));
 _GL_CXXALIASWARN (remainderl);
 #elif defined GNULIB_POSIXCHECK
 # undef remainderl

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 70
+# math_h.m4 serial 71
 dnl Copyright (C) 2007-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -230,6 +230,7 @@
   REPLACE_NAN=0;               AC_SUBST([REPLACE_NAN])
   REPLACE_REMAINDER=0;         AC_SUBST([REPLACE_REMAINDER])
   REPLACE_REMAINDERF=0;        AC_SUBST([REPLACE_REMAINDERF])
+  REPLACE_REMAINDERL=0;        AC_SUBST([REPLACE_REMAINDERL])
   REPLACE_ROUND=0;             AC_SUBST([REPLACE_ROUND])
   REPLACE_ROUNDF=0;            AC_SUBST([REPLACE_ROUNDF])
   REPLACE_ROUNDL=0;            AC_SUBST([REPLACE_ROUNDL])

new file mode 100644
--- /dev/null
+++ b/m4/remainderl-ieee.m4
@@ -0,0 +1,15 @@
+# remainderl-ieee.m4 serial 1
+dnl Copyright (C) 2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl This macro is in a separate file (not in remainderl.m4 and not inlined in the
+dnl module description), so that gl_FUNC_REMAINDER can test whether 'aclocal'
+dnl has found uses of this macro.
+
+AC_DEFUN([gl_FUNC_REMAINDERL_IEEE],
+[
+  m4_divert_text([INIT_PREPARE], [gl_remainderl_required=ieee])
+  AC_REQUIRE([gl_FUNC_REMAINDERL])
+])

--- a/m4/remainderl.m4
+++ b/m4/remainderl.m4
@@ -1,4 +1,4 @@
-# remainderl.m4 serial 1
+# remainderl.m4 serial 2
 dnl Copyright (C) 2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,7 @@
 
 AC_DEFUN([gl_FUNC_REMAINDERL],
 [
+  m4_divert_text([DEFAULTS], [gl_remainderl_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
   AC_REQUIRE([gl_FUNC_REMAINDER])
@@ -34,8 +35,56 @@
   LIBS="$save_LIBS"
   if test $gl_cv_func_remainderl = yes; then
     REMAINDERL_LIBM="$REMAINDER_LIBM"
+    m4_ifdef([gl_FUNC_REMAINDERL_IEEE], [
+      if test $gl_remainderl_required = ieee && test $REPLACE_REMAINDERL = 0; then
+        AC_CACHE_CHECK([whether remainderl works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_remainderl_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $REMAINDERL_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+/* Compare two numbers with ==.
+   This is a separate function because IRIX 6.5 "cc -O" miscompiles an
+   'x == x' test.  */
+static int
+numeric_equal (long double x, long double y)
+{
+  return x == y;
+}
+static long double dummy (long double x, long double y) { return 0; }
+int main (int argc, char *argv[])
+{
+  long double (*my_remainderl) (long double, long double) = argc ? remainderl : dummy;
+  long double i;
+  long double f;
+  /* Test remainderl(...,0.0L).
+     This test fails on OSF/1 5.1.  */
+  f = my_remainderl (2.0L, 0.0L);
+  if (numeric_equal (f, f))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_remainderl_ieee=yes],
+              [gl_cv_func_remainderl_ieee=no],
+              [gl_cv_func_remainderl_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_remainderl_ieee" in
+          *yes) ;;
+          *) REPLACE_REMAINDERL=1 ;;
+        esac
+      fi
+    ])
   else
     HAVE_REMAINDERL=0
+  fi
+  if test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; then
     dnl Find libraries needed to link lib/remainderl.c.
     if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
       REMAINDERL_LIBM="$REMAINDER_LIBM"

--- a/modules/math
+++ b/modules/math
@@ -200,6 +200,7 @@
 	      -e 's|@''REPLACE_NAN''@|$(REPLACE_NAN)|g' \
 	      -e 's|@''REPLACE_REMAINDER''@|$(REPLACE_REMAINDER)|g' \
 	      -e 's|@''REPLACE_REMAINDERF''@|$(REPLACE_REMAINDERF)|g' \
+	      -e 's|@''REPLACE_REMAINDERL''@|$(REPLACE_REMAINDERL)|g' \
 	      -e 's|@''REPLACE_ROUND''@|$(REPLACE_ROUND)|g' \
 	      -e 's|@''REPLACE_ROUNDF''@|$(REPLACE_ROUNDF)|g' \
 	      -e 's|@''REPLACE_ROUNDL''@|$(REPLACE_ROUNDL)|g' \

--- a/modules/remainderl
+++ b/modules/remainderl
@@ -8,13 +8,13 @@
 
 Depends-on:
 math
-remainder       [test $HAVE_REMAINDERL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1]
-roundl          [test $HAVE_REMAINDERL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
-fmal            [test $HAVE_REMAINDERL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
+remainder       [{ test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; } && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1]
+roundl          [{ test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; } && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
+fmal            [{ test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; } && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
 
 configure.ac:
 gl_FUNC_REMAINDERL
-if test $HAVE_REMAINDERL = 0; then
+if test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; then
   AC_LIBOBJ([remainderl])
 fi
 gl_MATH_MODULE_INDICATOR([remainderl])

--- a/modules/remainderl-ieee
+++ b/modules/remainderl-ieee
@@ -2,12 +2,15 @@
 remainderl() function according to ISO C 99 with IEC 60559.
 
 Files:
+m4/remainderl-ieee.m4
 
 Depends-on:
 remainderl
 fpieee
+remainder-ieee  [{ test $HAVE_REMAINDERL = 0 || test $REPLACE_REMAINDERL = 1; } && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1]
 
 configure.ac:
+gl_FUNC_REMAINDERL_IEEE
 
 Makefile.am: